1. Field of the Invention
The present invention relates to district heating pipes for potable water which contain a polymeric composition which has particular utility for hot water pipe service. In particular, the present invention relates to a polymeric composition comprising a butene-1 homopolymer and a particular group of additive components.
2. Description of the Prior Art
Since its introduction in the United States in the early 1970's, the major market for butene-1 polymers has been in hot water extruded pipe applications. For the most part, these prior art butene-1 polymer compositions comprised a butene-1 polymer along with various standard antioxidants. In these plumbing applications, the flexibility of the butene-1 polymers, its good creep resistance over a wide range of temperatures and high hydrostatic design stress rating were very useful properties. However, one drawback of the prior art polybutylene plumbing resins is the deactivation of stabilizer due to hot water aging, leading to partial loss of stability. Especially for more demanding applications such as district heating where the pipes are continuously exposed to hot water, improvements were required in the prior art plumbing grade resins. The present invention deals with a combination of ingredients in a butene-1 polymer composition that is a significant improvement in the art.